An Athlete’s Heart

With sudden cardiac deaths in local races, there’s a need to understand the changes that take place in your heart when you do endurance sports. BY Nina C. Beltran, MD

Athletes are thought to be the healthiest segment of the population and are believed to be impervious to illnesses. But why are there instances of athletes—seeming to be in perfect health—having heart attacks or sudden cardiac death (SCD)?

What happens to our hearts when we train for endurance or strength? Is it true that athletes are more prone to SCD and arrhythmia (irregular heartbeats) than non-athletes? Or is this a reporting bias, because more cases are coming to light about athletes with cardiovascular problems?

Athletic Heart Syndrome

Let me first introduce you to the notion that exercise does effect a change in our heart’s structure. Our heart is a muscle. Any muscle that is stressed or working hard often enlarges (like our biceps, when we do curls).

The subtle changes in our hearts when we do endurance (more than five hours per week) or strength training cause small increases in the size of the ventricles (pumping chamber) and atrium (filling chamber) with increased thickness of the heart muscle. The blood vessels from the heart also increase—these are all adaptive changes to allow our hearts to be able to supply blood and oxygen to exercising tissues. Heart rates of athletes also tend to slow down; the resting heart rate, can go down to less than 60 beats per minute to maximize amount of blood to be ejected per beat. This is called Sinus Bradycardia, quite universal in athletes. This is why sometimes, the heart rate is a reasonable approximation of cardiovascular fitness.

All these changes could also be regarded as the workout’s training effect on the heart because the level of physical activity determines the changes the heart makes.

These adaptive changes, when they occur, are called Athletic Heart Syndrome. This is also known as Athlete’s Heart, Exercise-induced Cardiomegaly, or Athletic Bradycardia. Take note that these are not medical conditions or diseases. These are normal, expected changes of a heart that is experiencing athletic training.

How do I know if I have an Athlete’s Heart?

When you have Athletic Heart Syndrome, most often you do not have any physical symptoms; just a consistently low resting heart rate (40-60 beats per minute). Signs of having this syndrome are bradycardia, cardiomegaly, and cardiac hypertrophy.

Athlete’s Heart is usually diagnosed by your doctor on routine screening or checkups for other medical concerns. If you are an athlete, you may have an enlarged heart. This can be seen in a simple chest x-ray or 2D echocardiogram. Sinus bradycardia can be appreciated by physical examination or electrocardiogram (ECG). This is often accompanied by sinus arrhythmia (irregular heart beat). The pulse of an athlete may sometimes have skipped beats or have irregularities at rest but should return to normal after exercise begins.

Athlete’s Heart is not dangerous for athletes. Since it doesn’t pose any significant threat, no treatment is required.

Arrhythmia in Athletes

Anything done in excess may cause harm. Extreme endurance exercise done for prolonged period of time and in high-level intensity increases risk of cardiac arrhythmia. This physical change that occurs in an athlete’s heart due to prolonged and intense physical activity is called ventricular remodelling. Sometimes, these changes can be not-so-subtle to cause serious arrhythmia. However, most studies on athletes’ hearts do not show any increased risk of having cardiovascular events such as heart attacks and strokes. Some athletes who do have cardiac problems already have other underlying structural heart disease all along.

This is why we cannot stress enough that an athlete should see a doctor and get clearance to be sure if the signs and symptoms — such as bradycardia, irregular heart beat, and enlargement of the heart, are due to just an Athlete’s Heart and not another heart disease.

Why? This is because an Athlete’s Heart is very similar to a heart condition called Hypertrophic Cardiomyopathy (HCM). This heart problem is genetic or hereditary and has structural abnormalities. They are characterized by an enlarged heart or bradycardia, and a person suffering from either of the two suffers fainting spells or loss of consciousness, or sometimes can exhibit no symptoms at all. It is important to distinguish between an Athlete’s Heart and Hypertrophic Cardiomyopathy since HCM is a serious cardiovascular disease that is a leading cause of sudden cardiac death.

Overall, an individual with an Athlete’s Heart still enjoys lower overall mortality rates compared to non-exercising individuals. The fact that exercise is good still remains unchanged and unchallenged. The lifestyle of an endurance athlete means good health because they have less body fat and better eating habits, and stay away from smoking and alcohol.

Intense and long-term endurance training may increase the risk for arrhythmia, but it doesn’t mean athletes should avoid the sports they love. It’s just a gentle reminder to have yourself checked by your friendly doctor to be on the safe side and to enjoy a worry-free workout.

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Author

is a doctor specializing in Internal Medicine and Pulmonology. She is also a member of the medical students' Sports Development Committee in UERM and a speacker for Nutrition for Endurance Athletes for the Philippine College of Physicians. She has been doing triathlons for two years now with the Aboitiz Multisport Team and Team Tribe.